The Ouellette lab is interested in the consequences of reductive evolution on bacterial physiology. As Chlamydia has adapted to an intracellular niche, it has lost many genes that are present in free-living bacteria. These genes/gene pathways that have been lost through reductive evolution (Muller’s Ratchet) typically encode metabolic pathways to synthesize, for example, amino acids. Since Chlamydia relies on its host cell for many nutrients, it is not surprising that it would eliminate these types of genes. However, Chlamydia has also eliminated genes that are considered essential for viability or pathogenesis in many other bacteria. This raises many interesting questions that are the focus of Dr. Ouellette’s research as described below. Conversely, when Chlamydia has retained genes that are atypical for Gram-negative bacteria (e.g. genes normally found in Gram-positive bacteria), this is also interesting and suggests a function that is important to chlamydial growth otherwise these genes would have been deleted.
Image of McCoy cells infected with C. trachomatis L2. Arrows indicate chlamydial inclusions within cells. Each inclusion is filled with hundreds of individual organisms.